Various forms of imaging apparatus have been used extensively for medical applications. For example, fluoroscope systems, X-ray imaging systems, ultrasound imaging systems, computed tomography (CT) imaging systems, and magnetic resonance (MR) imaging (MRI) systems have been used for a number of years. Any number of medical examination, interventional procedures, diagnosis, and/or treatment may be provided using an appropriate one of the foregoing systems suited for the task.
Ultrasound imaging systems have been used as a tool for assisting interventional clinical procedures and medical examinations. For example, conventional two-dimensional (2D) ultrasound imaging has been used in the field of regional anesthesia to provide a way of “seeing” and tracking the delivery of the anesthetic with a needle, rather than attempting to achieve such a goal blindly using nerve stimulation technology. Additionally, 2D ultrasound imaging has been used by medical practitioners for examination of various regions of interest within a patient's body, such as to view anatomical structures (e.g., cardiac, pulmonary, gastrointestinal, and other structures), in utero fetuses, tumors, and the like.
Ultrasound imaging technology has developed to a point that high quality 2D images are provided and image frame rates are relatively high. For example, transducer arrays are often used to sweep ultrasonic beams across an image plane to form high quality images. Various processing techniques have been developed to reduce speckle, sharpen edges, etc. However, the planar, vertical “slice” views typically provided by such 2D ultrasound imaging has not always provided practitioners with a desired view of the target. For example, particular structure of interest is often difficult to identify from a planar slice through that structure. Often, a view of a surface of a target structure is desired, which is often impossible or very difficult using traditional 2D ultrasound imaging techniques.
Computing technology, having progressed dramatically in the last few decades, has provided the ability to produce three-dimensional (3D) (e.g. a dataset providing information in an X, Y, and Z axes space) and even four-dimensional (4D) (e.g., a 3D image having a time axis added thereto) volume images. Ultrasound volume imaging (3D, 4D, real-time 3D, etc.) has seen increasing use with respect to medical procedures and medical examinations, especially OB/GYN and cardiac examinations. An advantage of volume imaging, is that with volume imaging it is possible to generate views of a region or target of interest, such as baby face and heart chambers, which are readily recognizable to the user. Using volume imaging techniques it is possible to reconstruct and visualize any arbitrary plane or even surface within the image volume that is not otherwise obtainable by 2D imaging.
However, the 3D and 4D imaging technology typically used in volume imaging arose from disciplines such as drafting, modeling, and even gaining, thus the technology has primarily been adopted for use in the medical field rather than having been developed uniquely for use in the medical field. Similarly, imaging transducer technology used with respect to 3D and 4D imaging (e.g., single beam mechanical single beam wobbler ultrasound transducers and matrix array ultrasound transducers) has primarily been adopted from 2D transducer technology. A disadvantage of volume imaging is its much slower volume rate compared to 2D imaging frame rates. For example, the volume rate in volume imaging is often limited by the size of the volume, acoustic imaging rate, and ultrasonic beam sweeping rate (e.g., the mechanical moving rate for a wobbler probe or the beam forming rate of a matrix array). Moreover, volume imaging techniques often suffer from degraded image quality for any arbitrary plane, especially the elevation plane if the volume is obtained by a wobbler transducer. For example, image quality is often limited, when a wobbler transducer is used, by a single-element beam providing poor sampling of the elevation plane and, when a matrix array transducer is used, by the limited number of elements of the matrix array (e.g., 32 to 64 compared to 128 to 256 elements for standard array transducer) and sparse beams in 3D space.